Detection of plants is important in agricultural technology, in which context mention shall be made of so-called phenotyping of plants. A further example of detection is identification of plants so as to enable, for example, automatic weeding, or removal of undesired plants, i.e. weeds.
Various methods are commonly used for three-dimensional detection of objects, such as stripe light methods or light section methods. Said methods offer high spatial three-dimensional resolution. However, with regard to illumination, they are dependent on defined ambient conditions. A further disadvantage is that three-dimensional detection cannot be performed within a very short time.
With stripe light methods, various light patterns need to be projected onto the object successively, whereas light section methods comprise detecting only one contour line at any given point in time. Thus, for three-dimensional detection, the object has to be scanned.
For generating the defined light conditions on a field, one may set up a tent which keeps the ambient light from the area to be detected. Then a defined ambient condition may be created within said light-proof tent so as to apply the light section method or the stripe light method. Once a specific area located within the tent is done with, the tent has to be taken down and set up again at another location, whereupon the light section method or the stripe light method may be applied again at said other location.
This approach is time-consuming and therefore expensive. Also, it is not suitable for three-dimensional detection of relatively large areas, since this procedure is too slow. To achieve sufficient throughput, a very large number of light section teams would have to work in parallel, which necessitates a large number of tents, a large number of light section cameras and, therefore, a large demand for qualified skilled labor, all of which leads to an increase in cost.
On the other hand, it is very important, in particular for developing plant seeds, to obtain, at regular intervals, such as every week to every other week, an objective assessment of the seedlings produced from one type of seeds without said seedlings being destroyed. It shall be noted that in this context, such fields may be used as test fields which have a minimum size so as to have reasonably realistic growth conditions. Therefore, if one intends to have large cultivation areas for one type of seeds, relatively large test areas will be necessitated.
What is necessitated in addition to test areas of significant sizes is precise data on the spatial alignment of plant leaves, on the size of the plant leaves, on the structure of the plant leaves, etc., in order to obtain accurate information about a specific type of seeds. To reliably obtain said information when the plants may not be torn out, three-dimensional detection is necessitated, since with two-dimensional detection, only projections or silhouettes of leaves are detected, but their alignment cannot be determined, and their true surface area also cannot be determined because one cannot deduce the surface area itself from a projection without having any knowledge of the alignment of the projected area.